The present invention relates to a roller fitted around a bushing of a conveyor chain used for conveyance of bottles, cans, precision parts, paper containers, sushi serving plates and so on, or of a chain used for cower transmission, and also to a chain equipped with such roller.
A conveyor chain such as a top chain used for conveyance of sushi serving plates along a circulation path is mainly formed from engineering plastic or stainless steel. According to the structure, the top chain is generally classified into two types; one being of the xe2x80x9crollerxe2x80x9d type which has a roller mounted on a bushing at the link joint portion of a base chain, and the other being of the xe2x80x9cbushxe2x80x9d type which has no roller mounted on a bushing (see, Japanese Utility Model Laid-open Publication No. (SHO) 62-98615 and Japanese Utility Model Publication No. (HEI) 2-31456, respectively).
FIG. 3 shows in top plan view a part of the conventional roller type top chain formed from a plastic material. The top chain 31 comprises a crescent-shaped top plate 32 and a base chain 33. FIG. 4 shows a link element of the top chain 31, which is formed by an offset link. As shown in perspective view in FIG. 5, an upper link 34 and an inner bushing tube 35 are formed integrally with each other, and a lower link 36 and an outer bushing tube 37 are formed integrally with each other. The inner bushing tube 35 is fitted in the outer bushing tube 37 so as to form a link assembly 38. The inner and outer bushing tubes 35 and 37 jointly form a bushing portion having a separable structure. When the inner bushing tube 35 is inserted in an axial hole 37A of the outer bushing tube 37, a generally annular locking projection 35A formed on the tip end of the inner bushing tube 35 is snap-fit or otherwise interlocked with an annular recessed portion (not shown) formed continuously with a closed end portion (lower end portion in FIG. 5) of the axial hole 37A. The inner bushing tube 35 has an axial slit 35B extending at least across the locking projection 35A so as to facilitate elastic deformation of the locking projection 35A when the locking projection 35A is forced into the axial hole 37A of the outer bushing tube 37.
In the manufacture of the top chain 31, a roller 40 is rotatably mounted on the outer bushing tube 37, as shown in FIG. 5, before the inner bushing tube 35 is fitted in the outer bushing tube 37 to complete the link assembly 38. The top plate 32 and the link assembly 38 are then connected together by a metallic connector pin 41. A top chain 31 is thus formed. In the top chain 31, the base chain 33 connected with the link assembly 38 constitutes an offset chain. The top plate 32 and the upper link 34 are integrally molded of a synthetic resin. Alternatively, the upper link 34 may be firmly fitted between parallel spaced locking projections (not shown) formed on the undersurface of the top plate 32 in either case, the upper link 34 and the top plate 32 are firmly connected together against separation. In FIGS. 3 to 5, reference characters 32A, 34A and 36A denote pin holes for receiving therein the metallic connector pin 41.
FIG. 6 shows in perspective view a part of the conventional bush type top chain. This top chain is substantially the same as the roller type top chain 31 previously described, with the exception that it does not have a roller. In the bush type ton chain, a link assembly having a bushing portion 39 is connected to a top plate 32 by a connector pin 41. The bushing portion 39 has a separable structure composed of inner and outer bushing tubes assembled together in the same manner as described above. The bushing portion 39 may be formed integrally with upper and lower links 34, 36.
As a conveyor chain, a generally known bush chain is used. The bush chain (not shown) comprises a series of link assemblies each having two inner links connected together by two bushings formed integrally therewith, and a series of sets of outer links arranged alternately with the link assemblies and articulately connected to the link assemblies by means of connector pins extending through the bushings. In one form, each of the link assemblies may be molded from a synthetic resin into an one-piece or unitary structure, and the outer links may be made of metal and disposed on the opposite outer sides of the link assembly so as to form a chain.
In the conventional roller type top chain, the upper link 34 and the lower link 36 are structurally independent from each other, and the bushing portion has a separable structure composed of an inner bushing tube 35 and an outer bushing tube 37. The inner and outer bushing tubes 35, 37 are engaged together merely by an interlocking engagement between the locking projection 35A formed on the tip end of the Inner bushing tube 35 and a recessed portion (not shown) formed continuously with the lower end portion of the axial hole 37A of the outer bushing tube 37. The interlocking engagement between the inner and outer bushing tubes 35, 37 may be released, so that the conventional roller type top chain is inferior in strength and rigidity of the bush portion to a chain having link assemblies each formed of two links connected together by two bushings formed integrally therewith. Accordingly, when the conventional roller type top chain is subjected to a great tensile force, the bushing portion may be damaged, resulting in reduction of the service life of the top chain. Another problem is that when a great tensile force is applied to the top chain, the upper and lower links 34, 36 of each link assembly 38 tend to spread or move apart in vertical direction about the bushing portion 35, 37, and the amount of deformation of the top chain in the vertical direction increases with spreading of the links 34, 36, accordingly. Since the direction of spreading movement of the upper and lower links 34, 36 substantially coincides with the axial direction of the connector pin 41, removal of the connector pin is likely to occur, which may cause accidental disassembly of the top chain.
To deal with the foregoing problems, attempts have been made to form two links and a single bushing integrally with each other to form a single link assembly or to form two links and two bushings integrally with each other to form a single link assembly. However, the link assemblies thus formed make it impossible to mount a roller on the bushing portion.
The conventional bush type top chain is generally used with a sprocket disposed on each corner portion of a circular path of the chain. The sprocket and parts required to install the sprocket make the bush type top chain complicated in construction. Additionally, the bush type top chain requires a larger installation space than the roller type top chain because the roller type top chain can be guided only by horizontal rails without using sprockets. In view of the space requirement, horizontal guide rails disposed at a corner portion may be used with the bush type top chain. However, as opposed to rolling contact achieved between the roller type top chain and the horizontal guide rail, sliding contact achieved between the bush type top chain and the horizontal guide rail creates a greater frictional resistance, and the tensile force acting on the bush type top chain increases accordingly.
It is an object of the present invention to provide a roller which is capable of being mounted on a link assembly of a strong and rigid one-piece structure composed of two links and one or more bushing members formed integrally with the links.
Another object of the present invention is to provide a chain which is highly resistant against damage even when subjected to a great tensile force, has a roller capable of being mounted on a bushing portion with utmost ease, and can be manufactured with improved efficiency.
In one aspect, the present invention seeks to provide a roller for a chain including a link assembly having two links and a bushing formed integrally with the links, wherein the roller comprises a split roller composed of two roller segments assembled together so that the roller can be rotatably mounted on the bushing from a radial direction of the bushing.
In another aspect the present invention seeks to provide a chain comprising: a number of link assemblies connected by pins, each of the link assemblies having two links and a bushing formed integrally with the links; and a roller rotatably mounted on the bushing of each of the link assemblies, the roller comprising a split roller composed of two roller segments assembled together to mount the bushing rotatably on the bushing from a radial direction of the bushing.
Preferably, the roller segments have an identical configuration.
In one form of the present invention, the roller segments are hinged at one circumferential end thereof and snap-fitted at the other circumferential end thereof.
In another form of the present invention, the roller segments are snap-fitted at opposite circumferential ends thereof.
One end in the circumferential direction of each roller segment is partially removed to form a first stepped portion facing in one direction along the axis the roller, and the other end in the circumferential direction of the same roller segment is partially removed to form a second stepped portion facing in the opposite direction along the axis the roller. The first stepped portion has a locking projection formed thereon, and the second stepped portion has a retaining recess snap-fit with the locking projection on the first stepped portion of another roller segment. Preferably, the opposite ends in the circumferential direction of each roller segment each have a semicircular convex surface extending in the axial direction of the roller, and the first and second stepped portions each have a semicircular concave surface extending in the axial direction of the roller, the semicircular convex surface being complementary in contour to the semicircular concave surface.
As an alternative, each of the roller segments may have straights joint surfaces formed at opposite circumferential ends thereof and extending diametrically across the roller, wherein one end in the circumferential direction of each roller segment has a plug projecting from the joint surface, and the other end in the circumferential direction of the same roller segment has a socket recessed from the joint surface and lockingly receiving therein the plug of another roller segment. Preferably, the plug has two aligned locking projections projecting from opposite surfaces of the plug in the axial direction of the roller, and the socket has two aligned retaining recesses extending in the axial direction of the roller and opening at one end to opposite surfaces of the socket, the retaining recesses being snap-fit with the corresponding locking projections of another roller segment.
The roller comprised of a split roller composed of two roller segments connected together can be mounted on a bushing of a link assembly from a radial outward direction even though the link assembly has a one-piece structure including two links formed integrally with the bushing. This improves the manufacturing efficiency of a chain in which the roller is used. The one-piece link assembly is superior in strength. The roller mounted on the bushing insures rolling contact at a corner portion of a chain circulating path, so that the friction resistance during conveyance is very small. This enables the chain to be applied to a longer conveyor.